A Messy Forecast

Late update here on a Saturday night.  There's been some big changes since yesterday's blog post, so I wanted to fill you in.  As expected, the rain has arrived tonight, and it looks like we're in for a soaking.  Through Sunday night, much of the region is expected to rack up 1-2" of additional rainfall.  Here's the latest rainfall forecast graphic (6PM Sat-6PM Sun):


Along with this rain, a strong cold front will move through by Sunday morning, causing winds to shift to the NNW and temperatures to drop as the day wears on.  We'll drop to the mid 40's overnight, then fall to near 40 by Sunday at dusk.

The big change since yesterday is that the "closed-low scenario" that forecast models had gone back and forth on appears to be happening after all, which will have a major impact on our Monday & Tuesday weather.  Instead of getting back to dry weather, things will stay cold and wet until Wednesday.  Before I go into more details on the forecast, let's looks at what I mean by a "closed low".

At some point you've probably heard us discuss troughs and ridges....ridges are associated with high pressure, troughs with low pressure.  Usually cold fronts and unsettled weather accompany a trough, which is certainly the case this weekend.  Here's a look at a forecast model showing a large trough across the central U.S. as of Sunday AM:

See the big dip with the bright colors that looks like a "V"....that's the trough, sometimes called an "open wave".  As this trough deepens and evolves, it will develop into a closed low by Monday morning. Here's what that looks like on the models:

Notice how the white lines have closed off?  There's your closed low.  These are also sometimes called "cold core lows".  The ultimate result of this low is that it will keep moisture flowing in from the east, and at least on the western side of the low, will pull in colder air from the north.  This means rain chances will continue into Monday and Tuesday.  It also means that some of us may see our first snowflakes of the year.  Let's check out another model chart...

I know they are a little tough to see, but look at the dotted red and blue lines on this chart.  Those are atmospheric thickness lines.  Without getting too technical, they basically give an indication of temperatures, and where you see the blue lines, that is sort of a "quick glance" check of where it is cold enough for frozen precip to form....something we call the "540 line".  Sure enough, right in the very same region as our closed low, we find the 540 line, and a chance for rain to mix with or change over to snow.  Based on the forecast position of the low, it looks like the coldest air will be found over southeast MO & northwest TN, and thus the best chance for some flakes Sunday night and Monday.  There may also be a little mixing or a changeover again Monday night and Tuesday morning.

As far as the snow portion of the forecast, this is really only a big deal simply because it's the first chance of snow this season.  With warm ground temperatures, there's no reason to think anything will stick, and any snow that does fall won't amount to much anyway.  So no reason to go buy bread and milk...unless you just need some!  The rainfall portion of the forecast is a different story.  By the time this system moves out Tuesday night, many of us will have added another 2-4" to rain gauges that have already measured a lot of rain this month.  Before the beginning of tonight's rain, we had 9.25" here at the station this month, and the NWS Paducah had 7.48".

Rain This Weekend...And More???

Hello everyone!  I hope you had a wonderful Thanksgiving, and got some good deals if you were one of those dedicated Black Friday shoppers.  Cheesy as it sounds, I've been advertising today's weather as a "one-day only deal", with big discounts on cloud cover leading to lots of sunshine, and mild temperatures in the lower 60's as a free gift! 

Unfortunately, the pleasant weather ends tomorrow, as a strong cold front will be sweeping across the central U.S., bringing widespread rain, winds, and colder temperatures.  Here's what our weather map will look like by tomorrow at 6PM:

A cold front will be in the process of moving through the region, bringing widespread rain to the Local 6 region.  Rain could arrive as early as sunrise in southeast MO, but the highest rain chances will run from around midday through the evening.  This will be another steady, soaking rain once it sets in, with pretty hefty totals expected, especially the farther east you go.

Rainfall totals through 6AM Monday (seen above) should reach near an inch across southern IL & southeast MO, and should range from 1-2" across western KY & northwest TN.  Even heavier amounts are expected from central KY into middle TN and northern MS & AL, where 3 or 4 inches will be possible.  This will certainly dampen the drive home across much of the mid-south over the holiday weekend, and may end up causing several delays at airports across the eastern U.S.

As this front continues to press east Saturday night and Sunday, colder air will quickly fill in....and if the cold air can catch up to the moisture quick enough, a few spots across the eastern U.S. could see a few snowflakes.  The next two graphics show where snow may fall....however, I'm going to include a disclaimer that based on some of the model data I looked at, I think these forecasts are a bit overdone. 

The graphic above shows the probability of at least 1" of snow through 6AM Sunday.  Notice parts of southern IL & west KY are being shown in the 40-80% range.  Again, I think this is too high.  With this system moving east pretty quickly, I think most of the deep moisture is out of here before the cold air can arrive.  We may have a couple of sprinkles or flurries Sunday, but I believe most of the day will be dry. Moving on, here's the same graphic for the next day:

This graphic for the probability of at least 1" of snow runs from 6AM Sun-6AM Mon.  I do think it is more possible to see some flakes flying farther to our east, but shouldn't amount to much.

So, bottom line....rain is almost a certainty for Saturday, but should end by Sunday morning, with only a very slim chance of a few flurries mixing in on the tail end of this system.

Beyond this weekend, the majority of forecast models continue to be in agreement that this system will clear out by Monday & Tuesday, giving us mainly clear skies.  However, there is at least one model still indicating a slower departure to this system, so I'm not ready to fully commit to sunshine for Mon/Tue...we'll go with partly cloudy for now.  Temperatures next week will be turning colder, with daytime highs from Sunday-Thursday not likely to get above 50.  Overnight lows through that same period will run in the neighborhood of 30. 

A quick scan of the extended 8-16 day charts shows a pretty uneventful beginning to December, with little to no precipitation showing up, and temperatures running pretty close to seasonal norms.

11/11/11...A Historic Storm

Greetings!  Tomorrow is a special day on the calendar....it's 11-11-11, the perfect palindrome!  This is coming on the heels of another numerically special date a little over a week ago, which was 11-02-2011, another palindrome.  Aside from being a once-in-a-century day on the calendar, there is also some interesting weather history that occurred 100 years ago, on 11-11-1911. 

One of the most dramatic drops in temperature ever recorded occurred during the late afternoon and evening hours in what is known as The Great Blue Norther of 1911.  A fast-moving and very powerful cold front was sweeping south from the Northern Plains with no warning.  Many midwestern towns enjoyed blue skies and set record highs during the afternoon, with residents leaving their coats and jacket behind to enjoy a final taste of summer-like weather.  Afternoon temperatures across Missouri rose to 76 in Kansas City, 78 in St. Louis, 80 in Springfield, and 82 in Columbia. 

However, as late afternoon arrived, those blue skies began to look violent....

As the clouds rolled in, winds quickly became violent, with hurricane-force winds accompanying the cold front.  Some locations reported violent thunderstorms, and even tornadoes with this system.  In fact, farther north, a tornado tore through much of the town of Owosso, MI, and according to records, struck around 11PM on 11-11-11.  It is now referred to as the "Tornado of the Elevens".

Owosso, MI...notice the caption on the photo that reads "11 P.M. 11-11-11"

In just a matter of an hour or two after the arrival of this front, temperatures dropped some 40 to 60 degrees, and rain and hail turned to sleet and snow.  The automatic temperature trace from Springfield, MO, shows a drop of nearly 60 degrees in 2 hours.

Springfield, MO temperature trace:  Record high of 81 just before 4PM, dropping to 24 at 6PM, and a record low of 10 at midnight.

For more reading on this historic weather system, here are a few links from other sources:

University of Missouri:  http://cafnrnews.com/2011/10/midwests-perfect-storm/

NWS Springfield:  http://test.crh.noaa.gov/sgf/?n=event_1911nov11_user1

NWS St. Louis:  http://www.crh.noaa.gov/lsx/?n=11/11/1911coldsnap

A Look Ahead....Stormy, Then Colder?

Greetings!  As expected, our Thursday got off to a wet start, with around 0.55" of rain here at the weather center.  It was an upside-down almanac day too....with our high temperature for the day of 60 degrees coming at 3AM, and a 45 degree reading as of this update at 4PM serving as our low for the day.  The upper-level low responsible for today's gray skies will shift off to the east tonight and tomorrow, bringing a return to sunshine to the area by our Friday afternoon.  In the wake of this upper-low, a nice ridge will build in for the weekend, allowing temperatures to moderate back into the upper 60's for daytime highs, with plenty of sunshine. 

7AM Sat.-Large ridge over Mid MS Valley, developing trough over the Rockies

By the first part of next week, we'll enter into a more unsettled pattern just in time for Election Day, as a storm system that will develop over the weekend across the Rockies begins to push eastward.  This will set us up for the potential for some stormy weather on Tuesday and Wednesday.

7AM Tuesday-Strong trough over the central Plains, putting our region in strong SW flow, leading to warm, moist air setting the stage for showers and thunderstorms.

This system will approach the region Tuesday, and bring a surface low and attendant cold front through the region Wednesday, leading to showers and perhaps some thunderstorms.  The Storm Prediction Center is including parts of southern Missouri and Arkansas in a risk for severe weather, so we'll want to keep an eye on the development of this system to see if parts of the Local 6 region may have to deal with strong storms as well.

 Storm Prediction Center's 4-8 Day Severe Weather Outlook

Behind this system, temperatures again look like they will fall into the 50's for highs and 30's for lows by the end of next week.  But, it's what might be on the way about two weeks from now that really caught my attention earlier today when looking through some longer-range forecast models.  A blast of cold air coming down from Canada may finally bring the first freeze to the region, with temperatures in the upper 20's being advertised by the morning of Thu. Nov. 17.

7AM, Thu., Nov. 17-GFS Surface temperature map showing readings in the upper 20's across the Local 6 region.

One thing to note, in my last blog I included some info on first freeze dates, and if freezing temperatures do not arrive until the 17th, it would set the record for the latest first freeze....with the previous latest date coming on Nov. 13, 1975.  We'll see what happens on the specifics, but one thing is for sure, cold air is coming, like it or not!